Dryer ventilation



April 9, 1968 R. A. DAANE DRYER VENTILATION Filed Dec. 6, 1966 JWP n NQH H INVENTOR.

fiaez fl fiawzze ATTORNEYS Patented Apr. 9, 1968 3,376,653 DRYERVENTILATION Robert A. Daane, Rockford, Ill., assignor to Beloit,Corporation, Beloit, Wis., a corporation of Wisconsin Filed Dec. 6,1966, Ser. No. 599,542 Claims. (Cl. 34-23) ABSTRACT OF THE DXSCLOSUREThe mechanism or embodiment shown in the drawings has an upper tier ofdryer drums such as 11 and a lower tier of drums such as 10 with a web Wpassing sinuously up and down between the drums and an upper belt B anda lower belt such as B passing over the webs on the drums and beingguided by belt guide rolls such as 16 and 19 positioned so that pocketssuch as 24 are formed which are filled with moisture. The drums aredriven so that the web moves at a speed in excess of two thousand feetper minute and air is pumped along the surface of the roll 16 into thepocket 24 and moist air is pumped .out

of the pocket as shown by the arrow 37. Moist air is separated from theguide roll by a vane 26 and fresh dry air can be supplied at with FIGURE2 having a second vane also for removing moist air.

The present invention relates broadly to the art of papermaking and ismore particularly directed to a new and improved means for removingmoisture from pockets formed between runs of paper web formed in a dryersection.

In the dryer section of a paper machine the moisture bearing web isdirected along a serpentine path in wrapping relation with dryingcyli-nders which are arranged in tiers, with a typical arrangementhaving an upper and lower tier. As the web passes up and down pocketsare formed between the surface of the web with the moist air in thepockets retarding the escape of moisture from the web. The presence ofthe vaporized moisture or high humidity in the pocket retardsevaporation and if the humidity .of the air in this pocket can bereduced the rate of drying and efficiency of the machine will beenhanced.

It is accordingly an important object of the present invention toprovide an improved method and mechanism for removing moisture frompockets formed between runs .of web in a drum type paper dryer.

A further object of the invention lies in the provision of a method andmechanism for removing vapor in pockets in a dryer section with the useof substantially less equipment than heretofore available requiring lessspace for operating mechanism and avoiding the necessity of complicatedducts, bores and other equipment heretofore employed.

A feature of the invention is the provision of the belt which passesover the Web holding it against the dryer FIGURE 1 is a schematic endelevational view showing a drier section embodying the principle of thepresent invention;

FIGURE 2 is a fragmentary schematic view illustrating another form .ofthe invention;

FIGURE 3 is an enlarged fragmentary plan view showing a portion of thebelt.

A paper web w such as is received from the press section of a papermachine passes into the dryer section to be carried over a series ofcylindrical dryer drums illustrated in sequence at 10, 11, 12, 13, 14and 15. While only a portion of the dryer section is shown the web willpass sequentially in a serpentine fashion over more drums until it isdry.

The drums are suitably heated such as by steam to increase thetemperature of the moisture for rapid evaporation and the moisture vaporis carried away by ventilation systems. As is known to those versed inthe art the more rapidly the humid air can be carried away from thesurface of the web, the more rapidly the drying process will ensue.

As the web w travels up and down between the dryer drum arrangementpockets are formed between the runs of the web and since the moisture ofthe web is hot evaporation will continue and the humidity within thepockets is extremely high. If this humidity level can be reduced theevaporation rate within the pockets will increase thereby increasing theefficiency of the dryer and reducing the amount of dryer space necessaryto provide in a mill.

As illustrated in FIGURE 1, the dryer drums are arranged in tiers withthe upper tiers being represented by the drums 11, 13 and -15 and thelower tier represented by the drums 10, 12 and 14.

It has heretofore been practice to hold the web firmly against thesurface of the dryer drum by a felt which engages the outer surface ofthe web during the time it passes .over the drum. These felts orcanvasses can accommodate movement of air but are relatively imperviousrequiring air to be forced therethrough. Attempts have heretofore beenmade to exchange the air within the pockets formed between the web toreduce the humidity therein but these devices have required provision ofsubstantial equipment. An example of this type of structure is shown inthe Patent 3,110,575 wherein means are provided by blowers directing airinto a plenum chamber to force air through the felt on one side of theguide roll and to provide a suction to withdraw air through the feltdrums which is formed of a porous or pervious material accommodating thefree passage of air and guiding the belt between the drums over a guideroll, driving the equipment at a surface speed in excess of two thousandfeet per minute so that the guide roll pumps air through the belt intothe pocket and pumps air out of the pocket through the belt to provide acontinual exchange of air in the pocket during operation, with the moistair carried along the surface .of the guide roll being removed by a vanemeans and replaced with dryer air.

Further objects, advantages and features of the invention will becomemore apparent with the disclosure .of the preferred embodiments thereofin the specification, claims and drawings in which,

As shown on the drawings:

.on the other side of a guide roll.

In accordance with the present invention a belt formed of a highlypervious fabric is providedwherein the fabric is formed of amonofilament material accommodating the free passage of air, andillustrated generally in FIGURE 3, this fabric or screen used to form anupper belt 12 and lower belts b and b".

Between the drums belt guide rolls 16 and 17 are provided to guide thebelts and maintain the tension thereon so that they function to hold theweb against the drums 11, 13 and 15. In the lower tier of drums, thefirst belt b is guided by the belt guide rolls 19 and 20 and a secondbelt b" passes over guide rolls 21 and 22. As will be seen in FIGURE 1the pockets between the web runs are formed at 23, 24 and 25.

The web w travels at a speed determined by the speed of rotation of thedrums and several means are provided for driving the drums illustratedschematically by the motor 9. Generally each of the drums areinterconnected and driven at a controlled speed as will be appreciatedby those skilled in the art and the mechanism need not be shown indetail.

It has been discovered that by utilizing the air pervious screen-likebelt, and driving the web at a speed in excess 3 of two thousand feetper minute, air will be pumped through the belts by the pumping actionof the guide rolls and the moving surfaces.

As illustrated for the pocket 24, a dryer is carried along the surfaceof the guide roll 16 and is pumped through the belt b in a directionindicated by the arrowed lines 35. This air flowing along the arrowedline 35 enters the pocket 24 and becomes moist during the evaporation ofmoisture from the Web. The moist air is pumped out of the pocket asindicated by the arrowed lines 37, passing through the pervious belt b.

The air is skimmed to remove it from the surface of the guide roll 16 bya separation means shown in the form of a generally radially extendingvane 26 which guides the moist air upwardly and out of the region of theroll 16. This permits dryer air to enter at the other side of the vane26 to flow down into the space and be picked up by the travellingsurface of the roll 16. A slight positive pressure is created in the nipformed between the felt b and the roll 16 and this positive pressurepumps the air through the pervious belt 12.

In some instances it may be desired to provide a specific supply of dryair along the space opposite the belt 12 in advance of the belt guideroll 16, and this is provided by air supply duct 30 which has aplurality of openings on its lower surface to direct the flow of dry airinto the space and onto the free surface of the belt guide roll 16.Other ducts 31, 32, 33 and 34 are provided for other pockets.

This arrangement accommodates the direct passage of air in a machinedirection into and out of the pocket and eliminates cross machine flowwhich has heretofore been present in ventilation systems and which havecaused flutter of the sheet or web. The arrangement also provides asimplified less expensive, less space consuming structure thanheretofore used.

FIGURE 2 illustrates another form of the invention which provides foreven more eflicient action and in the arrangement shown upper and lowertiers of dryer drums are provided with a web w-1 passing successivelyover dryer drums 40, 41 and 42. A porous or pervious belt 12-1 isprovided which accommodates the free passage of air and is positioned tohold the web onto the drums 40 and 42. The belt b-l passes over a beltguide roll 43 between the drums and a moisture entrapping pocket 54 isformed between the web runs.

As the mechanism operates, air is pumped by the surface of the guideroll 43 through the belt as indicated by the arrow 50. Air is pumped outof the pocket 54 as indicated by the arrowed line 52. In addition to thepumping action of the guide roll 43 the flow of air into the pocket 54is aided by the induced flow of air carried along the surface of thedrum, as indicated by the arrowed line 49. Movement of air of the pocketis also aided by the induced flow of air carried along with the web asindicated by the arrowed line 53.

Aair which carries along the surface of the guide roll 43 through thebelt b-1 is removed from the surface of the guide roll by a foil means44 which is generally in the form of a foil or vane with an edge closeto the outer surface of the roll 43. The vane 44 forms part of a box orcompartment 47 which contains fresh air delivered along the roll to flowthrough a wall 46 of the compartment which is provided with openings asindicated by the arrowed flow lines 51. This fresh dry air then passesdown through the belt along the path of the arrowed lines 49 and 50.

In addition to the first foil 44, a second foil 45 is provided which hasan edge extending close to the surface of the belt b-l as it is carriedalong on the drum 40. Moist air induced to flow along with the belt isremoved or skimmed from the surface of the belt as indicated by thearrowed line 48. This prevents this moist air from being carried down topass into the pocket 54. Thus only fresh dry air provided from thecompartment 47 passes down through the previous belt b-l.

Thus it will be seen that I have provided an improved ventilationarrangement for a dryer which meets the objectives and advantages aboveset forth. The mechanism does not consume an excessive amount of space,greatly enhances the drying speed and thus the efficiency of the dryerand avoids the necessity of power and spaceconsuming mechanism which hasheretofore been thought necessary.

The drawings and specification present a detailed disclosure of thepreferred embodiments of the invention, and it is to be understood thatthe invention is not limited to the specific forms disclosed, but coversall modifications, changes and alternative constructions and methodsfalling within the scope of the principles taught by the invention.

I claim as my invention: 1. A drying mechanism for a paper machinecomprisa plurality of tiers of drying drums including an upper tier anda lower tier for having a web trained there through with a web passingsinuously between the upper and lower tiers, upper and lower beltsformed of a pervious material accommodating the free passage of airtherethrough and being positioned against the web in the upper and lowertiers respectively while the web is trained over the drums,

belt guide rolls between the dryer drums in each of the tiers carryingthe belts between roll with pockets being formed between the web andbelt between the tiers containing moisture evaporated from the web,

means driving the drums at a surface speed in excess of two thousandfeet per minute so that the travelling surface of the rolls pumps a fiowof air through the pervious belts,

means positioned adjacent the surface of the guide rolls in an area freeof belt engagement causing separation of moisture laden air pumpedthrough the belt from the pocket whereby dryer air replaces the moistair against the surface of the roll to be pumped through the belt intothe pocket.

2. A drying mechanism for a paper machine in accordance with claim 1wherein said separation means includes a a vane extending generallyradially away from the guide roll between dryer drums so that moist airis pumped by the guide roll along a surface of the vane and dryer air ispumped along the other surface of the vane by movement of the guide rollsurface.

3. A drying mechanism for a paper machine comprising a plurality ofcylindrical dryer drums positioned to lead a travelling web to be driedthrough a drying path, means for driving said drums at a surface speedin excess of two thousand feet per minute, a web carrying beltpositioned to engage the surface of the web on the drums for maintainingthe web in heat transfer engagement and being pervious to the freepassage of air therethrough, belt guide rolls between the drums carryingthe belt between adjacent drums as the web is separated therefrom,

said guide roll surfaces and the surface of the belt inducing a flow ofair through said pervious belt, and means deflecting the moist airpassing through the belt off the free surface of the roll so that themoist air flows radially outwardly and dry air follows the roll surfaceand flows through the belt. 4. A drying mechanism for a paper machine inaccordance with claim 1 wherein means are provided for guide rollopposite the surface free of the belt after the moisture laden air hasbeen removed therefrom by said separation means.

5. A drying mechanism for a paper machine in accordance with claim 1wherein said separation means includes a first vane means positionedadjacent the surface of the guide roll moving moisture laden airtherefrom after it has been pumped through the belt and includes asecond vane means positioned adjacent the surface of the belt as it iscarried by a drum prior to passing over the guide roll so that moistureladen air is deflected off the surface of the belt before it passes ontothe surface of the guide roll.

6. A drying mechanism for a paper machine in accordance with claim 5wherein means is provided supplying dry air between said first andsecond vane means.

7. A drying mechanism for a paper machine in accordance with claim 1wherein said separation means includes an air supply compartment havinga wall forming a first vane means separating air from the guide rollafter it is pumped through the pervious belt with said compartmentadapted to contain a supply of dry air and having openings fordelivering air to the nip formed between the oncoming porous belt andthe guide roll, and said separation means including a second vane meansextending close to the surface of the drum in advance of the guide rollso that moisture laden air is separated from the belt before it passesonto the guide roll and wherein said second vane means joins thecompartment so as to provide a closed area for receiving the dry air.

8. In the method of drying a travelling web passing sinuously betweenupper and lower tiers of drying drums with upper and lower belts forholding the webs onto the drums and having guide rolls positionedbetween the drums of each tier for guiding the belts with pockets beingformed between the belts and the runs of web as they pass between thetiers, the method including the steps of providing a pervious beltcapable of accommodating a free passage of air, driving the drums at aspeed so that the web and roll surface will move at a speed in excess oftwo thousand feet per minute and so that the surface of the roll willpump air through the belt into and out of the pocket, and removing airfrom the surface of the roll where it is exposed and free of the belt sothat moist air is removed from the roll surface as it is pumped throughthe belt out of the pocket and dryer air will form on the surface of theroll to be carried through the belt into the pocket.

9. In the method of drying a travelling web in accordance with claim 8including the steps of furnishing a supply of dryer air into the nipbetween the roll and belt in advance of the belt moving into the pocket.

10. In the method of drying a travelling web in accordance with claim 8and including the step of removing moist air from the surface of thebelt on a drum in ad- Vance of the roll and carrying the moist air awayso that it will not mix with the dryer air entering the pocket.

References Cited UNITED STATES PATENTS 1,199,394 9/1916 Liebeck 34-1111,660,640 2/ 1928 Asten 34-111 3,110,575 11/1963 Justus 34111 3,325,9096/1967 Clark 34-111 XR KENNETH W. SPRAGUE, Primary Examiner.

